Method of manufacturing printed circuit board

ABSTRACT

Embodiments of the invention provide a method of manufacturing a printed circuit board. The method includes the steps of mounting a strip substrate on a fixing member, and separating the strip substrate into unit substrates by performing a singulation process. The method further includes the steps of attaching solder balls onto the unit substrates using a mask disposed on the unit substrates, and fixing the solder balls on the unit substrates by performing a reflow process.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of and claims the benefit of and priority to U.S. patent application Ser. No. 12/730,128, entitled, “METHOD OF MANUFACTURING PRINTED CIRCUIT BOARD,” filed on Mar. 23, 2010, which claims priority under 35 U.S.C. §119 to Korean Patent Application No. KR 10-2009-0117251, entitled “FABRICATING METHOD OF PRINTED CIRCUIT BOARD,” filed on Nov. 30, 2009, which are hereby incorporated by reference in their entirety into this application.

BACKGROUND

1. Field of the Invention

The present invention relates to a method of manufacturing a printed circuit board.

2. Description of the Related Art

Since densification, thinness, miniaturization and electrical improvements are being demanded by semiconductor packages, a substrate is becoming thinner and an electronic component-embedded substrate in which an electronic component is mounted and protected is being increasingly used. However, as the substrate becomes thinner, there is a problem in that the supporting force of the substrate is decreased, and thus the warpage thereof is increased. In particular, an electronic component-embedded substrate is problematic in that, after it is encapsulated with an epoxy molding compound (EMC), it becomes warped because of the difference in the thermal expansion coefficient. Therefore, owing to the increase in the warpage of a substrate, it is difficult to accurately attach solder balls at the predetermined positions of the substrate.

FIGS. 1A to 1E are sectional views showing a conventional method of manufacturing a printed circuit board. Hereinafter, conventional problems will be described with reference to FIGS. 1A to 1E.

First, as shown in FIG. 1A, a strip substrate 1 is provided. Here, the strip substrate 1 may be an electronic component-embedded substrate on which an electronic component is encapsulated with an epoxy molding compound (EMC) 5. This strip substrate 1 becomes warped because of the difference in thermal expansion coefficient between the substrate and the EMC 5.

Subsequently, as shown in FIG. 1B, flux 2 is applied onto the strip substrate 1. Here, since the strip substrate 1 is warped, there is a problem in that the flux 2 is not accurately applied at the predetermined positions of the strip substrate 1.

Subsequently, as shown in FIG. 1C, solder balls 3 are attached to the strip substrate 1. Here, the solder balls 3 are attached using a jig. In this case, since the strip substrate 1 is warped, there is also a problem in that the solder balls 3 are not accurately attached at the predetermined positions of the strip substrate 1, and collect at the specific parts of the strip substrate 1.

Subsequently, as shown in FIGS. 1D and 1E, a reflow process and a singulation process are performed. In the reflow process, the solder balls 3 are fixed through heat treatment, and, in this procedure, the strip substrate 1 is additionally warped. Therefore, since the solder balls 3 are not accurately attached at the predetermined positions of the strip substrate 1 and the strip substrate 1 becomes additionally warped through the reflow process, when the strip substrate 1 is separated into unit substrates 4 through the singulation process, there are problems in that the solder balls 3 are not accurately attached at the predetermined positions of each of the unit substrates 4, and each of the unit substrates 4 is also considerably warped.

Further, the conventional method of manufacturing a printed circuit board is uneconomical because expensive equipment is required and equipment suitable for the strip substrate 1 must be provided whenever the kind of strip substrate 1 is changed. Although technologies for attaching solder balls using a screen printing process have been developed, these technologies are also difficult to be practically used when the strip substrate 1 is warped because the screen printing process premises that the strip substrate is flat.

Therefore, various solutions for decreasing the warpage of the strip substrate 1 have been proposed, but most of the solutions are problematic in that they require high production cost and are difficult to be put into practical use due to the change in the raw material and design of the substrate.

SUMMARY

Accordingly, embodiments of the invention have been devised to solve the above-mentioned problems, and embodiments of the present invention provide a method of manufacturing a printed circuit board, in which solder balls are accurately formed at predetermined positions by attaching the solder balls after performing a singulation process.

An embodiment of the invention provide a method of manufacturing a printed circuit board, including mounting a strip substrate on a fixing member, separating the strip substrate into unit substrates by performing a singulation process, attaching solder balls onto the unit substrates using a jig, and fixing the solder balls on the unit substrates by performing a reflow process.

According to an embodiment, in the mounting of the strip substrate, the fixing member is dicing tape.

According to an embodiment, the method of manufacturing a printed circuit board further includes integrally mounting the unit substrates on a support plate before the attaching of the solder balls.

According to an embodiment, the support plate fixes the unit substrates by vacuum-adsorbing the unit substrates.

According to an embodiment, the method of manufacturing a printed circuit board further includes applying flux onto the unit substrates using a jig before the attaching of the solder balls.

According to an embodiment, the method of manufacturing a printed circuit board further includes applying flux onto the solder balls before the attaching of the solder balls.

According to an embodiment, the method of manufacturing a printed circuit board further includes mounting the unit substrates on a tray for reflow before the fixing of the solder balls.

According to another embodiment of the invention, there is provided a method of manufacturing a printed circuit board, including mounting a strip substrate on a fixing member, separating the strip substrate into unit substrates by performing a singulation process, attaching solder balls onto the unit substrates using a mask disposed on the unit substrates, and fixing the solder balls on the unit substrates by performing a reflow process.

According to an embodiment, in the mounting of the strip substrate, the fixing member is dicing tape.

According to an embodiment, the method of manufacturing a printed circuit board further includes integrally mounting the unit substrates on a support plate before the attaching of the solder balls.

According to an embodiment, the support plate fixes the unit substrates by vacuum-adsorbing the unit substrates.

According to an embodiment, the method of manufacturing a printed circuit board further includes applying flux onto the unit substrates using a mask disposed on the unit substrates before the attaching of the solder balls.

According to an embodiment, the method of manufacturing a printed circuit board further includes mounting the unit substrates on a tray for reflow before the fixing of the solder balls.

Various objects, advantages and features of the invention will become apparent from the following description of embodiments with reference to the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

These and other features, aspects, and advantages of the invention are better understood with regard to the following Detailed Description, appended Claims, and accompanying Figures. It is to be noted, however, that the Figures illustrate only various embodiments of the invention and are therefore not to be considered limiting of the invention's scope as it may include other effective embodiments as well.

FIGS. 1A to 1E are sectional views sequentially showing a conventional method of manufacturing a printed circuit board.

FIGS. 2, 3, 4A, 4B, 5, 6A, and 6B are sectional views sequentially showing a method of manufacturing a printed circuit board according to an embodiment of the invention.

FIGS. 7, 8, 9, 10, 11A, and 11B are sectional views sequentially showing a method of manufacturing a printed circuit board according to another embodiment of the invention.

DETAILED DESCRIPTION

Advantages and features of the present invention and methods of accomplishing the same will be apparent by referring to embodiments described below in detail in connection with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms. The embodiments are provided only for completing the disclosure of the present invention and for fully representing the scope of the present invention to those skilled in the art.

For simplicity and clarity of illustration, the drawing figures illustrate the general manner of construction, and descriptions and details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the discussion of the described embodiments of the invention. Additionally, elements in the drawing figures are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of embodiments of the present invention. Like reference numerals refer to like elements throughout the specification.

Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIGS. 2, 3, 4A, 4B, 5, 6A, and 6B are sectional views sequentially showing a method of manufacturing a printed circuit board according to an embodiment of the invention.

The method of manufacturing a printed circuit board, according to this embodiment, includes the steps of (A) mounting a strip substrate 100 on a fixing member 110, (B) separating the strip substrate 100 into unit substrates 200 through a singulation process, (C) attaching solder balls 130 onto the unit substrates 200 using a jig 140, and (D) fixing the solder balls 130 on the unit substrates 200 through a reflow process.

First, as shown in FIG. 2, a strip substrate 100 is mounted on a fixing member 110. Here, the strip substrate 100 is present in a state of having been warped due to the difference in the thermal expansion coefficient between a substrate and an epoxy molding compound (EMC) 105 and the decrease in thickness of a printed circuit board. Since a singulation process must be performed later in order to stretch the warped strip substrate 100, the strip substrate 100 is mounted on the fixing member 110. The fixing member 110 is not particularly limited as long as it stably supports the strip substrate 100 during a singulation process. Preferably, dicing tape is used as the fixing member 110.

Subsequently, as shown in FIG. 3, the strip substrate 100 is separated into unit substrates 200. The separation of the strip substrate 100 into the unit substrates 200 is performed by a general singulation process. The unit substrates 200 separated from the strip substrate 100 are maintained in a state in which they are integrally mounted on the fixing member 110, such as dicing tape, as an example. In this procedure, since the strip substrate 100 is separated into the unit substrates 200, the warpage of the strip substrate 100 is decreased. Thus, in the following procedure, flux 150 and solder balls 130 are accurately attached at the predetermined positions of the strip substrate 100.

Subsequently, as shown in FIGS. 4A and 4B, flux 150 is applied on the strip substrate 100. Here, flux 150 is a material which removes an oxide film from a substrate pad made of, for example, copper and chemically activates the substrate pad such that solder balls 130 easily attach to the substrate pad. The flux 150 is applied onto the pads of the unit substrates 200, to which the solder balls are to be attached, using a jig 120 (refer to FIG. 4A) or are directly applied onto the solder balls using the jig 120 (refer to FIG. 4B). Meanwhile, when the flux 150 is applied onto the unit substrates 200 using the jig 120, since the warpage of the strip substrate 100 was previously decreased through a singulation process, the flux 150 are accurately applied at the predetermined positions of the unit substrates 200. However, this procedure does not have to be necessarily performed, and, particularly, in the case of a flux-free soldering process, this procedure may be omitted.

Subsequently, as shown in FIG. 5, solder balls 130 are attached onto the unit substrates 200. Here, the solder balls 130 serve to connect the unit substrates 200 with external circuits, such as a mother board and the like, and are attached onto the unit substrates 200 using a jig 140. Further, the solder balls 130 are temporarily attached onto the unit substrates 200 by the flux 150, and are completely fixed on the unit substrates 200 by a reflow process later. Since the warpage of the strip substrate 100 is previously decreased through a singulation process, the solder balls 130 are accurately attached at the predetermined positions of the unit substrates 200.

Meanwhile, the lead time is shortened by performing the step of applying the flux 150 onto the unit substrates 150 and the step of attaching the solder balls 130 onto the unit substrates 200 in a state in which the unit substrates 150 separated from the strip substrate 100 are integrally mounted on the fixing member 110. Further, at the time of applying the flux 150 and attaching solder balls 150, a support plate 160 is employed in order to provide bearing resistance to the unit substrates 200. Here, the support plate 160 fixes the unit substrates 200 by vacuum-adsorbing the unit substrates 200 through suction holes 165, so that the residual warpage of the unit substrates 200 are further decreased and the movement of the unit substrates 200 is prevented, with the result that the flux 150 is accurately applied at the predetermined positions of the unit substrates 200 and the solder balls 130 is accurately attach at the predetermined positions thereof. Further, according to an embodiment, the unit substrates 200 is mounted on the support plate 160 in a state in which they are integrally mounted on the fixing member 110.

Subsequently, as shown FIGS. 6A and 6B, the solder balls 130 are fixed on the unit substrates 200 by a reflow process. The reflow process is a process of solidifying the solder balls 130 by heating, melting and then cooling them. In this case, since the unit substrates 200 are also heated to high temperature, a heat-resistant tray 170 for reflow is employed. Thus, after the dicing tape previously used as the fixing member 110 is removed, the unit substrates 200 are mounted on the tray 170 for reflow, and then the reflow process is performed. The unit substrates 200 are mounted on the tray 170 for reflow using an adsorption nozzle.

However, when dicing tape having heat resistance is employed, the reflow process may be performed in a state in which the unit substrates 200 are mounted on the dicing tape without mounting them on the tray 170 for reflow.

Meanwhile, in this embodiment, differently from conventional technologies, since the reflow process is performed in a state in which the strip substrate 100 is separated into the unit substrates 200, the additional warpage of the strip substrate 100 occurring in the reflow process is reduced.

The method of manufacturing a printed circuit board, according to this embodiment, is advantageous in that the solder balls 130 are accurately formed at the predetermined positions of the strip substrate 100 because they are attached to the unit substrates 200 after the warpage of the strip substrate 100 was reduced by a singulation process. Further, the method of manufacturing a printed circuit board, according to this embodiment, is advantageous in that the manufacturing cost of a printed circuit board are lowered because the jigs 120 and 140 used to apply the flux 150 or to attach the solder balls 130 are used in the same way as before. Furthermore, the method of manufacturing a printed circuit board, according to this embodiment, is advantageous in that the lead time in this method does not differ from the lead time of the conventional method which is performed in a state in which the strip substrate 100 is not separated into the unit substrates 200 because this method is performed in a state in which the separated unit substrates 200 are integrally mounted on the fixing member 110 or the tray 170 for reflow.

FIGS. 7, 8, 9, 10, 11A, and 11B are sectional views sequentially showing a method of manufacturing a printed circuit board according to another embodiment of the invention.

The method of manufacturing a printed circuit board, according to this embodiment, includes the steps of (A) mounting a strip substrate 100 on a fixing member 110, (B) separating the strip substrate 100 into unit substrates 200 by a singulation process, (C) attaching solder balls 130 onto the unit substrates 200 using a mask 145 disposed on the unit substrates 200, and (D) fixing the solder balls 130 on the unit substrates 200 by a reflow process.

This embodiment greatly differs from the above-mentioned embodiment in a process of attaching solder balls. Therefore, the differences therebetween will be mainly described, and a redundant description thereof will be omitted.

First, as shown in FIGS. 7 and 8, a strip substrate 100 is mounted on a fixing member 110, and is then separated into unit substrates 200. Specifically, the strip substrate 100 is mounted on the fixing member, such as dicing tape, and then a singulation process is used to separate the strip substrate 100 into the unit substrates 200 in order to stretch the warped strip substrate 100.

Subsequently, as shown in FIG. 9, flux 150 is applied on the unit substrates 200. In this embodiment, differently from the above-mentioned embodiment, the flux 150 is applied on the unit substrates 200 using a screen printing process after a mask 125 is disposed on the unit substrates 200. More specifically, the flux 150 is applied on the unit substrates 200 by disposing the mask 125 provided with openings 127 on one side of the unit substrates 200 and then pressing the flux 150 onto the unit substrates 200 through the openings 127 using a squeegee. In order to accurately apply the flux 150 at predetermined positions of the unit substrates 200, it is preferred to suitably control the hardness, fixed angle, velocity and pressure applied to the substrate by the squeegee 129. In embodiments of the present invention, differently from conventional technologies, a screen printing process based on the premise that a printed circuit board is flat can be performed because the warpage of a printed circuit board was decreased through a singulation process. However, like the above-mentioned embodiment, this procedure may be omitted in the case of a flux-free soldering process.

Subsequently, as shown in FIG. 10, solder balls 130 are attached onto the unit substrates 200. Here, the solder balls 130, like the procedure of applying the flux 150, are applied on the unit substrates 200 using a screen printing process after a mask 145 is disposed on the unit substrates 200. More specifically, the solder balls 130 are applied on the unit substrates 200 by disposing the mask 145 provided with openings 147 on one side of the unit substrates 200 and then pressing the solder balls 130 onto the unit substrates 200 through the openings 147 using a squeegee. According to an embodiment, the solder balls 130 are attached at predetermined positions of the unit substrates 200 because a singulation process is used to decrease the warpage of a printed circuit board.

Meanwhile, as in the above-mentioned embodiment, the lead time is shortened by performing the step of applying the flux 150 onto the unit substrates 150 and the step of attaching the solder balls 130 onto the unit substrates 200 in a state in which the unit substrates 150 separated from the strip substrate 100 are integrally mounted on the fixing member 110. Further, at the time of applying the flux 150 and attaching solder balls 150, a support plate 160 is employed in order to provide bearing resistance to the unit substrates 200. The support plate 160 fixes the unit substrates 200 by vacuum-adsorbing the unit substrates 200 through suction holes 165, so that the residual warpage of the unit substrates 200 are further decreased and the movement of the unit substrates 200 is prevented, with the result that the flux 150 is accurately applied at the predetermined positions of the unit substrates 200 and the solder balls 130 are accurately attached at the predetermined positions thereof.

Subsequently, as shown FIGS. 11A and 11B, the solder balls 130 are fixed on the unit substrates 200 by a reflow process. In this embodiment, the reflow process is performed by mounting the unit substrates 200 on a heat-resistant tray 170 for reflow because the unit substrates 200 are heated to high temperature.

The method of manufacturing a printed circuit board, according to this embodiment, is advantageous in that a singulation process was previously performed to decrease the warpage of a printed circuit board, so that a screen printing process based on the premise that a printed circuit board is flat can be performed, thereby reducing the cost necessary for a high-priced apparatus, such as a flux dotting tool or the like.

As described above, the method of manufacturing a printed circuit board, according to various embodiments of the invention, is advantageous in that the solder balls are accurately formed at the predetermined positions of the strip substrate because they are attached to the unit substrates after the warpage of the strip substrate was reduced by a singulation process, and in that the additional warpage of the strip substrate occurring in a reflow process can be reduced because the reflow process is performed after the strip substrate is separated into unit substrates by performing the singulation process.

Further, the method of manufacturing a printed circuit board, according to various embodiments of the invention, is advantageous in that solder balls are attached to unit substrates using a screen printing method because a singulation process reduces the warpage of a strip substrate, and in that the expenditures necessary for a high-priced apparatus, such as a flux dotting tool is reduced because the screen printing method is used.

Furthermore, the method of manufacturing a printed circuit board, according to various embodiments of the invention, is advantageous in that it can also be used in a wafer leveling process.

Terms used herein are provided to explain embodiments, not limiting the present invention. Throughout this specification, the singular form includes the plural form unless the context clearly indicates otherwise. When terms “comprises” and/or “comprising” used herein do not preclude existence and addition of another component, step, operation and/or device, in addition to the above-mentioned component, step, operation and/or device.

Embodiments of the present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.

The terms and words used in the present specification and claims should not be interpreted as being limited to typical meanings or dictionary definitions, but should be interpreted as having meanings and concepts relevant to the technical scope of the present invention based on the rule according to which an inventor can appropriately define the concept of the term to describe the best method he or she knows for carrying out the invention.

The terms “first,” “second,” “third,” “fourth,” and the like in the description and in the claims, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Similarly, if a method is described herein as comprising a series of steps, the order of such steps as presented herein is not necessarily the only order in which such steps may be performed, and certain of the stated steps may possibly be omitted and/or certain other steps not described herein may possibly be added to the method.

The singular forms “a,” “an,” and “the” include plural referents, unless the context clearly dictates otherwise.

As used herein and in the appended claims, the words “comprise,” “has,” and “include” and all grammatical variations thereof are each intended to have an open, non-limiting meaning that does not exclude additional elements or steps.

As used herein, the terms “left,” “right,” “front,” “back,” “top,” “bottom,” “over,” “under,” and the like in the description and in the claims, if any, are used for descriptive purposes and not necessarily for describing permanent relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in other orientations than those illustrated or otherwise described herein. The term “coupled,” as used herein, is defined as directly or indirectly connected in an electrical or non-electrical manner. Objects described herein as being “adjacent to” each other may be in physical contact with each other, in close proximity to each other, or in the same general region or area as each other, as appropriate for the context in which the phrase is used. Occurrences of the phrase “according to an embodiment” herein do not necessarily all refer to the same embodiment.

Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.

Although the present invention has been described in detail, it should be understood that various changes, substitutions, and alterations can be made hereupon without departing from the principle and scope of the invention. Accordingly, the scope of the present invention should be determined by the following claims and their appropriate legal equivalents. 

What is claimed is:
 1. A method of manufacturing a printed circuit board, comprising: mounting a strip substrate on a fixing member; separating the strip substrate into unit substrates by performing a singulation process; attaching solder balls onto the unit substrates using a mask disposed on the unit substrates; and fixing the solder balls on the unit substrates by performing a reflow process.
 2. The method of manufacturing a printed circuit board according to claim 1, wherein, in the mounting of the strip substrate, the fixing member is dicing tape.
 3. The method of manufacturing a printed circuit board according to claim 1, further comprising: integrally mounting the unit substrates on a support plate before the attaching of the solder balls.
 4. The method of manufacturing a printed circuit board according to claim 3, wherein the support plate fixes the unit substrates by vacuum-adsorbing the unit substrates.
 5. The method of manufacturing a printed circuit board according to claim 1, further comprising: applying flux onto the unit substrates using a mask disposed on the unit substrates before the attaching of the solder balls.
 6. The method of manufacturing a printed circuit board according to claim 1, further comprising: mounting the unit substrates on a tray for reflow before the fixing of the solder balls. 